1. Field of the Invention
The present invention relates to a method for actuating a switch element of a valve device.
2. Description of the Related Art
The published German Patent Application document DE 10 2008 054 512 A1 describes a fuel injection system of an internal combustion engine having a piston fuel pump. The delivery rate thereof is adjusted by a fuel-supply control valve. It includes an inlet check valve that can be positively held in the open position thereof at the beginning of a delivery stroke by a solenoid actuated tappet. As long as this is the case, the fuel does not reach a high-pressure area of the fuel system, but rather is returned to a low-pressure area.
In the case of a normally open fuel-supply control valve, the tappet is pressed by a spring against the valve element, whereas, in response to energization, an electromagnetic actuating device urges the tappet away from the valve element. To reduce the operating noises for a normally open fuel-supply control valve, the published German Patent Application document DE 10 2008 054 512 A1 discusses retarding a movement of the tappet in the direction of the valve element shortly before the tappet strikes a limit stop, by briefly supplying current to the electromagnetic actuating device, thus a “braking pulse.” It has been found, however, that it is important that this braking pulse be very precisely timed. The beginning of the braking pulse is defined by the end of what is generally referred to as a “pause period,” which, in turn, begins at the start of extinction of a preceding magnetization of a coil of the electromagnetic actuating device. The beginning of the braking pulse, respectively the end of the pause period should correspond very precisely to a specified value to allow the braking pulse to achieve the optimal effect thereof.
Due to the different manufacturing tolerances of the components of the piston fuel pump and of the fuel-supply control valve, the mechanical properties of the tappet, as well as the electrical properties of the electromagnetic actuating device sometimes deviate from the theoretical nominal case. The result can be that, without countermeasures, the braking pulse is no longer generated at the optimum point in time. Therefore, the published German Patent Application document DE 10 2008 054 512 A1 discusses adapting the pause period by utilizing a correlation between the pickup and dropout characteristics of the tappet to perform a correction.